In general, in vehicles such as a four-wheeled vehicle, a hydraulic shock absorber is provided as a cylinder device between each wheel (axle side) and a vehicle body so as to damp vibration of the vehicle (see, for example, Patent Literature 1). A related-art cylinder device of this type includes a hydraulic stopper mechanism configured to cause a hydraulic cushioning effect at maximum extension of a piston rod so as to prevent full extension.